Currently, 3D printing, and in particular fused deposition modeling (FDM), employ constant extrusion temperature (θdie) and head velocity (V), as shown in FIG. 1. The level of control currently available in FDM is similar to that in other 3D printing techniques, such as laser sintering.
Because the processing parameters remain constant, there is limited control of the interfacial healing. When the filament, which is typically 1-3 mm in diameter, is deposited on the substrate, the temperature of the substrate affects the degree of welding or healing of the interfaces. For example, if the filament (or powder) is deposited onto a substrate that is relatively cold, the temperature of the extruded filament should be relatively high to assure proper welding/healing of the interface. If the filament's temperature is too low, a lack of fusion may result in poor healing and weak parts. In contrast, if the substrate is relatively hot because of the residual heat from the printing process (that is, the printing head recently printed this particular area), the temperature of the extruded filament should be reduced to prevent overheating, which could lead to excessive squeeze flow, lack of dimensional part control, and thermal degradation of the material.
Interfacial healing is the fundamental mechanism that governs additive manufacturing, such as 3D printing. When two surfaces made from the same polymer are brought together in the molten state, the surfaces will conform to each other to achieve intimate contact, and over time intermolecular diffusion and chain entanglement result in fusion bonding or welding of the surfaces to each other. The degree of healing or welding is based on many parameters, including material properties, temperature, interfacial pressure, and time. It has been shown that during healing and welding, five separate phases can be identified, the more critical ones being heating, squeeze flow, and cooling. It has also been proposed and showed that polymer motion can be described by reptilian motion. In general, welding/healing of two polymer interfaces occurs either quickly at a relatively high temperature, or slowly at a relatively low temperature, because interfacial healing is a diffusion process.
Testing has shown that the only process parameter that can effect weld quality (part quality) in 3D printing is extrusion temperature. However, because of thermal inertia of the metal extrusion die, it is not possible to vary the temperature fast enough to allow weld quality to be controlled.
Therefore there is a need in the art to provide an apparatus, system, and/or method for 3D printing that allows for near instantaneous control of the extrusion temperature of a supplied printing material to control the weld quality of the printed component.